Three homologous azobenzene (Az)-containing urea amphiphiles having two, one, and no hydrogen(s) at the terminal nitrogen of urea were synthesized by stepwise substitutions with methyl group(s). The spreading behavior, molecular packing, and photomechanical response of the Langmuir monolayers on water were investigated together with a homologous carboxylic acid derivative. The film stability, packing state, and photoreactivity that leads to photomechanical responses were clearly categorized into two groups: (1) the urea amphiphiles having two and one hydrogen(s) at the molecular end and (2) the urea amphiphile with no hydrogen at this position. The properties of the latter monolayer resembled that of the carboxylic acid homologue. Most likely, such distinct changes are attributable to the difference in the mode of the intermolecular hydrogen bond, namely, whether the bifurcated hydrogen bonds that are typically found in urea derivative assemblies can be formed. This work presents a typical example that the minimum chemical modification definitely alters the molecular functions in the assembled state.